1. Field of the Invention
The present invention relates to an improved heart valve prosthesis for use in improving the function of the mitral and/or tricuspid heart valves.
2. The Prior Art
The bicuspid or mitral valve is located in the left atrioventricular opening of the heart. It is encircled by a dense fibrous ring and consists of two valve leaflets of unequal size. The larger valve leaflet (called ventral or anterior cusp) is placed adjacent the aortic opening. The smaller leaflet is the dorsal or posterior cusp. The leaflets are composed of strong fibrous tissue which is thick in the central part but thin and translucent near the margin. The valves are constructed so as to pass blood unidirectionally from the left atrium to the left ventricle of the heart.
The tricuspid valve is located in the right atrioventricular opening and comprises three leaflets sometimes referred to as the anterior, posterior and septal cusps. The leaflets are roughly triangular in shape and attached to a fibrous ring with the apices projecting into the ventricular cavity.
Both the mitral and tricuspid valves are intended to prevent regurgitation of blood from the ventricle into the atrium when the ventricle contracts. In order to withstand the substantial back pressure and prevent regurgitation of blood into the atrium during the ventricular contraction, the cusps are held in place by delicate but strong fibrous cords which anchor the valve cusps to the muscular wall of the heart.
In some well recognized instances of heart disease, however, valve leaflet prolapse is evident. Prolapse of the valve leaflet appears to result from a dilatation or elongation of the posterior two-thirds of the valve annulus. A number of circumstances may cause the valve defect. The result of the defect, however, is the failure of normal apposition of the leaflets. When the leaflets fail to close completely during ventricular systole, the leaflets become damaged, the cords ruptured and the atrioventricular annulus distended. The result of the valve prolapse is a syndrome often associated with chest pain, cardiac arrythmias, dyspnea, and other adverse clinical symptoms.
One obvious solution to a serious valve prolapse is total valve replacement. It is generally agreed, however, that total valve replacement is too radical except in the most advanced cases. Accordingly, treatment of valve prolapse by techniques of annuloplasty have become more commonplace.
One of the more common annuloplastic techniques is schematically illustrated in FIG. 1 of the drawing and consists of suturing (plicating) the two valve leaflets together at the commissures so as to reduce the size of the opening through which blood can pass. The purpose of this suture is to draw the anterior and posterior cusps sufficiently close together that normal apposition will occur during ventricular systole. Experience has proved, however, that plication of the annulus at the commissures places extreme stress on the tissue adjacent the sutures with the unfortunate result that the sutures tear from the tissue damaging the leaflets and recreating the conditions susceptible to prolapse.
A valve prosthesis for mitigating the serious valve insufficiency described above is suggested by Carpentier in the Journal of Thoracic and Cardiovascular Surgery Volume 61, No. 1, January 1971. The prior art valve prosthesis described therein consists of a rigid circular or oval ring covered with a Teflon fabric which permits the ring to be sutured in place. The Carpentier ring was an improvement in many respects over earlier techniques. However, two inherent disadvantages in the Carpentier ring have become apparent. First, in order to secure the ring in place, suture placement is required along the anterior section of the annulus adjacent the aortic valve. Not infrequently, sutures are inadvertently passed into the aortic valve so as to interfere with the valve function. Moreover, to secure the rigid structure adjacent the largest (anterior) leaflet has the effect of interfering with mitral valve function. Second, with the passage of time sutures used for securing prior art prostheses may be subject to degeneration as a result of continual heart and valve action. Suture degeneration can result in separation of the prosthesis from its secured position causing at least partial failure of the prosthesis and risking interference with valve function.
Accordingly, it would be a significant improvement in the art to provide a heart valve prosthesis which restores valve function without interfering with adjacent valves and which would promote tissue adherence through natural fibroblastic growth and endothelization through natural processes so as to maintain the prosthesis securely in place. Such an improvement is disclosed and claimed herein.